Method of producing cyclobutanone

ABSTRACT

The invention relates to a process for preparing cyclobutanone by oxidizing cyclobutanol with an alkali metal hypochlorite or alkaline earth metal hypochlorite in the presence of an acid.

The invention relates to a novel process for preparing cyclobutanone.

It is known that cyclobutanone is obtained by oxidation of cyclobutanol.The processes which have been described employ customary organicoxidants such as various dialkyldioxiranes, chloral, tert-butylhydroperoxide or substituted or unsubstituted perbenzoic acids; ortransition metal or noble metal catalysts including their oxides andoxide complexes (cf., for example, React. Funct. Polym., 29 (2), 101-14,1996; Can. J. Chem., 62 (9), 1835-9, 1984; Org. Synth., 60, 20-5, 1981;and JACS, 96 (21), 6647-57, 1974).

For an industrial-scale process, the systems chromium(VI) oxide/oxalicacid and ruthenium oxide/sodium periodate are also possible from aprocess engineering point of view. However, these have the generaldisadvantage of an excessively high cost of the catalyst system (in thecase of ruthenium oxide) or the large amounts of waste and theirdisposal (in the case of chromium and iodine).

Further known common nonoxidative methods of preparation, e.g.photodecomposition, photooxidation or cyclization, with or withoutsubsequent hydrolysis of derivatives of carbonyl functions, are onlysuitable on a laboratory scale.

It has been found that cyclobutanone is obtained when cyclobutanol isoxidized by means of alkali metal hypochlorite or alkaline earth metalhypochlorite in the presence of an organic or inorganic acid as solvent.

The process of the present invention surprisingly makes it possible toobtain cyclobutanone in a simple manner in very good yields and in highpurity without the cyclobutane ring being expanded to butyrolactone in aBAYER-VILLIGER oxidation as main reaction and opened.

The reaction according to the invention thus has the advantage of asimple, inexpensive and environmentally friendly method of obtainingcyclobutanone, in particular on an industrial scale.

If, for example, the system aqueous sodium hypochlorite/acetic acid isused for the oxidation, the reaction in the process of the invention canbe represented by the following scheme:

Cyclobutanol as starting material is a generally known compound inorganic chemistry and is obtainable in a generally known manner, e.g. byreaction/ring expansion of cyclopropyl carbinol with concentratedhydrochloric acid (cf., for example, Org. Synth. 60, 20-25, 1981).

Preferred alkali metal and alkaline earth metal hypochlorites aresodium, potassium and calcium hypochlorites. The hypochlorites areusually used as aqueous solutions. The technical-grade solutions aregenerally suitable.

Preferred organic acids are alkanoic acids, in particular C₁-C₄-alkanoicacids such as acetic acid; preferred inorganic acids are mineral acids,in particular hydrochloric acid.

The aqueous sodium hypochlorite/glacial acetic acid system isparticularly advantageous.

The reaction temperatures in the oxidation can be varied within a widerange. In general, the oxidation is carried out at from −20° C. to +30°C., preferably from −20° C. to +20° C., particularly preferably from−10° C. to +10° C.

The work-up is carried out in a customary fashion; the pH may optionallybe kept in the slightly basic range by addition of alkali metalcarbonate or alkali metal hydrogencarbonate, in particular potassiumhydrogencarbonate or sodium hydrogencarbonate (cf. the preparativeexamples).

In one particular embodiment of the process of the invention thestarting material cyclobutanol can be prepared from cyclopropyl carbinolin the presence of acids, especially concentrated mineral acids, and thesubsequent oxidation to cyclobutanone can be conducted in a kind of“one-pot” reaction, i.e. in situ without isolating the intermediate orchanging the solvent (of the preparative examples).

The preparation of cyclobutanol from cyclopropyl carbinol is known perse. It is generally carried out in water as solvent in the presence ofacids, in particular mineral acids such as concentrated hydrochloricacid. Typical reaction temperatures are in the range from 20° C. to 120°C.; the reaction is generally carried out under reflux conditions.

The cyclobutanone to be prepared by the process of the inventionrepresents a key intermediate of general interest.

PREPARATIVE EXAMPLES Example 1

6.3 kg (76.1 mol; 84% pure) of cyclobutanol are dissolved in 23.6 l ofacetic acid while stirring and the solution is metered into 42 l ofaqueous sodium hypochlorite (13% active chlorine) at 0° C. to 5° C.(jacket temperature: −18° C.) over a period of 5 hours. The yellowishsuspension is stirred for 12 hours (overnight) at from 3° C. to 10° C.and subsequently stirred into 871 of water, resulting in a pH of 3.

The mixture is extracted with 2×30l and 2×16 l of methylene chloride,resulting in the aqueous phase becoming clear. The organic phase isstirred into 60 l of water, after which 6.9 kg of sodiumhydrogencarbonate are slowly (foaming!) added while stirring, resultingin a pH of 6. The aqueous phase is separated off, the organic phase isadmixed with 30 l of water, followed by addition of another 2.3 kg ofsodium hydrogencarbonate while stirring, bringing the pH to 8.

The organic phase is separated off and evaporated at 40° C. and 550-600mbar in a vessel. The residue (18.2 kg) is fractionally distilled in thedistillation laboratory.

This gives 3.52 kg (64.75% of theory) of cyclobutanone having a boilingpoint of 88° C./1750 mbar and a purity of 98% according to GC.

Example 2

73.1 g (1 mol) of cyclopropyl carbinol in 680 ml of water are admixedwith 100 ml of concentrated hydrochloric acid and refluxed for 3 hours.819 g of aqueous sodium hypochlorite (13% active chlorine) aresubsequently added dropwise to the reaction mixture at from 0° C. to 5°C. over a period of 3 hours, with the pH being kept at not more than 2(addition of hydrochloric acid if necessary). The mixture is stirredfurther for about 4 hours at from 0° C. to 5° C. and is extracted twicewith 250 ml each time of dichloromethane. The combined extracts areevaporated by distilling off the solvent and the residue is distilledunder atmospheric pressure.

This gives 59.4 g (84.7% of theory) of cyclobutanone having a purity of95.5% according to GC.

What is claimed is:
 1. A process for preparing cyclobutanone comprisingoxidizing cyclobutanol with an alkali metal hypochlorite or alkalineearth metal hypochlorite in the presence of an acid.
 2. A processaccording to claim 1 wherein the acid is a C₁-C₄-alkanoic acid.
 3. Aprocess according to claim 1 wherein the alkali metal hypochlorite issodium hypochlorite.
 4. A process according to claim 1 wherein theoxidation is carried out at a temperature of from −20° C. to +30° C. 5.A process according to claim 1 wherein the cyclobutanol is prepared byrearrangement of cyclopropyl carbinol in the presence of an acid andthen oxidized in situ to form cyclobutanone.